1. Field of the Invention
The field of invention relates to asphalt compositions for roofing, damp-proofing and water proofing and their use. More specifically, the field relates to sulfur-extended elastomer asphalt binders (SEEABs).
2. Description of the Related Art
During the manufacturing and processing of materials containing asphalt such as asphalt-coated aggregates and hot asphalt mixes, working temperatures above 300° F. can cause problems for workers and their equipment. At temperatures greater than 300° F., sulfur and sulfur compounds present in asphalt or bitumen mixes, including elemental sulfur and naturally present heteroatom organic compounds, begin to react with other constituents in the asphalt and with the oxygen in the air. One of the main products of these reactions is hydrogen sulfide gas, where free sulfur in hydrocarbon environments dehydrogenates hydrocarbons and forms hydrogen sulfide. Hydrogen sulfide in low quantities is an irritant but in high quantities it is toxic. Heated sulfur that oxidizes in the air forms sulfur dioxide. Sulfur dioxide has a noxious odor and is considered an air pollutant. Working in elevated conditions, including on top of metal roofing, or in confined conditions, including basements and pits, can concentrate and exacerbate the exposure to these unwanted byproducts. It is desirable to find an asphalt composition that is workable at temperatures below 300° F. for worker comfort and safety in addition to not releasing noxious chemicals into the environment.
Sulfur, especially “free” or elemental sulfur, is an abundant and inexpensive material. Elemental sulfur is a byproduct of non-sweet natural gas and petroleum processing. Sources of free sulfur include petroleum refineries and gas sweetening plants. Because of the quantity of sulfur extracted annually from natural gas and petroleum processes, many sulfur producers consider elemental sulfur a “waste” product. Others have attempted to use waste sulfur as an expander or filler for asphalt and bitumen compositions but only have obtained limited success. Therefore, it is also desirable to find commercial uses for elemental sulfur. Incorporating sulfur into commercial products can transform what many consider a waste product into a product that has practical value as an expander of the hydrocarbon resource supply.